1. Technical Field
The present disclosure relates generally to the field of surgical instruments. In particular, the disclosure relates to an endoscopic electrosurgical forceps that is economical to manufacture and is capable of sealing and cutting relatively large tissue structures. The present disclosure relates also to connection mechanisms to actuate the jaw members of a surgical instrument.
2. Background of Related Art
Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaws that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaws may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode to permit the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaws. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis, which may facilitate the transection of the sealed tissue. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al.
A bipolar electrosurgical forceps typically includes opposed electrodes disposed on clamping faces of the jaws. The electrodes are charged to opposite electrical potentials such that an electrosurgical current may be selectively transferred through tissue grasped between the electrodes. To effect a proper seal, particularly in relatively large vessels, two predominant mechanical parameters must be accurately controlled; the pressure applied to the vessel, and the gap distance established between the electrodes.
Both the pressure and gap distance influence the effectiveness of the resultant tissue seal. If an adequate gap distance is not maintained, there is a possibility that the opposed electrodes will contact one another, which may cause a short circuit and prevent energy from being transferred through the tissue. Also, if too low a force is applied the tissue may have a tendency to move before an adequate seal can be generated. The thickness of a typical effective tissue seal is optimally between about 0.001 and about 0.006 inches. Below this range, the seal may shred or tear and above this range the vessel walls may not be effectively joined. Closure pressures for sealing large tissue structures preferably fall within the range of about 3 kg/cm2 to about 16 kg/cm2.
Additionally, prior art surgical instruments include connection mechanisms for actuation of distal end components such as jaw members where the connection mechanisms require several manufacturing steps such as attaching a mandrel to an inner shaft member with corresponding number of parts required. Misalignment of the parts may result in an inconsistent and/or inadequate delivery of the shaft force required for actuation.
As is traditional, the term “distal” refers herein to an end of the apparatus that is farther from an operator, and the term “proximal” refers herein to the end of the electrosurgical forceps that is closer to the operator.